Glass filter



Dec. 8, 1942. F. A. BiGKFORD GLAS S F ILTER Filed Jan. 2, 1940 i FEED ,4. Brcwraai; BY f )1 and and constitute a considerable item of laboratory position across a passage contraction of give the desired degree Patented Dec. 8, 1942 UNITED "res ;PATENT OFFlCE GLASS FILTER A. Bicfiord. Corning, N. "2 7., assignor to (Jorning Glass Works, i'lorning, N.

ration of New York I, a corpo- Application January 2,19%, Serial No. 312,110

4 Claims. (Cl. 210-412) This application relates to glass filters and more particularly to filters formed from powdered glass for use in chemical laboratories.

Heretofore filters have been manufactured by grinding glass to a powder, screening the powder to separate particles of the desired'degree'of fineness and sintering the particles to form a porous coherent mass. found desirable to fuse such a filter into a. solid glassv vessel in the manner shown in United States Patent No. 1,620,815. While such filters have met with wide acceptance and use in chemical laboratories, it has been found that they certain inherent weaknesses of strength difilculties of use which are both annoying expense.

The object'ol provedform of filter structure which is strong and durable, easily manufactured, and of uniform reproduceable characteristics.

The above and features a disc of sintered glass powder whos'e edges have been coated with a finely divided adherent refractory powder and which is maintained in the walls of the vessel above and the present invention is an imin a glass vessel by the For certain purposes it has been filter discs into a glass 4 other objects are attained in I v my improved filter which includes among its the accompanying the tube. It has been similar processes.- I have found it desirable to coat these edges oi my filter plates with athin layer of finely powdered, highly refractory material such as aluminum oxide, ground sand, cordierite, silicon carbide, or magnesium oxide to prevent sealing of the disc to the glass body in subsequent assembly of the filter. This material may best be applied by spraying it on as a very drying, will leave a powcircumference of the disc thin slip which, upon dery layer about the which is in the neighborhood of ..001 of an inch When so treated, I introduce my body such as the illustrated tube i0 which is of approximately the same diameter as the disc and which has a slight contraction formed in in thickness.

figure, thereby producing a slight shoulder against which the disc H may hear. when so positioned, I heat the glass body in the vicinity of the disc Just to the point where it can be worked, and by means of suitable tools swage down the walls of the tube into contact with the periphery-oi the disc and on either side thereof sufiiciently to form a tight mechanical seal between the wall and the disc and retain the disc against-longitudinal displacement with found that the presence of the layer of finely powdered material it prevents iusion between the glass of the disc l4 and the below the plane of the disc and into contact with 7 its edge. These and readily app ent upon study of the drawing forming part of this specification in which:

. 1 The single figure is a vertical cross-section oi a filter structure embodying my invention. 1

According to my invention, glass of the desired chemical composition is first crushed and subsequently ground for a period sumcient to of porosity in the final filter plate. The powdered glass may then be molded or otherwise shaped into the desired form after which it is sintered into a coherentbody. For of discussion, a disc-shaped filter will be referred to. I have. found that the degree of porosity obtained in a given filter depends upon three things: the initial grain size of the material, the time during ed to sintering temperatures, and thesintering temperature itself. Temperatures will vary with the particular glass composition employed, but

will in general be longer and higher for the coarser filters made irom coarser grain size After the filter plates have been sintered into a porous coherent body, the edges may be slightly rounded and trued-up by grinding, scraping, or

other features will be moreing a tight Joint wall of the vessel while at the same time formwhich prevents leakage of the precipitate around the edges of the disc and between them and the vessel wall.

which it is heatstruction I have plate H and tube Id of material It acting as a cushlaboratory. apparatus have While most of the glasses normally used in a satisfactory resistance to chemical attack in solid form where little area is exposed to attack, these same glasses may have insufilcient resistance when finely divided with enormously increased surface area.

ion to absorb the. differential expansion of the parts while at the same time maintaining a tight seal-between the Still further advantages, are attributable to the construction. herein disclosed. Inasmuch as its walls, as shown at l2 in there is no fusion of the parts one with another, body and extending thereacross, identations in the temperatures employed in forming the arthe wall of said body maintaining said filter in ticle need not exceed the melting point oi the position in said body and a thinv layer of powfilter disc and, accordingly, the entire area oi the dered material of higher melting point than said disc as originally formed remains available for 6 body and filter retained in the space between said the passage of filtrate For this reason the cabody and said filter and preventing leakage pacity of a filter'may be accurately predetertherebetween.

mined and reproduced without substantial varia-' 3. A filter comprising a hollow glass body, a

.tion and a greater filtering capacity obtained for porous sintered glass filter plate positioned transa given sized unit than in prior art structures.- 10 ver sely within said body, sections of said body Similarly, since relatively low temperatures are being displaced on both sides of said plate to employed and there are no differential strains mechanically lock it in position within said body set up in the were by contraction of the parts on and a thinlayer oi powdered material having a cooling, prolonged annealing of the usual type higher melting point than the materials of said maybe eliminated without detriment to the com- 15 body and plate completely filling the space bepieted filter, tween the edge of said plate and the adjacent What is claimed is: wall of said body. 1. A filter comprising a tubular glass body, a 4. A filter comprising a hollow glass body, a

filter plate .formed of sintered particles of glass 81888 filter plate Positioned transversely W hin positioned within said glass body and extending 20 Said body and formed 0! a 81888 Of (Miami thereacross, said body having areas of reduced chemical composition from that of said body, diameter on either side of said plate mechansaid plate in retained I position by the disicaliy locking said plate in position within said placement ofs t d a a f th wall or said body, and a thin layer of powdered material or body adjacent said p a e, and a yer o nowhigher melting point than said body and plate 5 dered material of higher melting point than interposed between the edge of said plate and said body and plate coating the edge oi said said body and preventing leakage therebetween plate adjacent said body and completely filling I or fusion thereof. the space therebetween.

2. A filter comprising a hollow glass body, a porous sintered glass filter positioned within said 80 FRED A. BICKIORD 

